There are different ways of evaluating experiences lived across time. The --hedometer' paradigm in economics suggests that momentary impressions determine overall evaluations of experiences. There is a mounting empirical evidence for a simple Peak-End rule. Peak (the most extreme) and End (the very last) impressions have been shown to explain overall evaluations without the need to account for other impressions. I test the Peak-End rule using field data from university classrooms and lab data from image-viewing experiments, as well as explore its ability to predict post-experience mood valence. I elicit, using a novel guessing task, lay intuitions about overall evaluations of experiences. Finally, I demonstrate why decision-makers may find it difficult to learn the Peak-End rule and believe rather, that overall evaluations reflect average impressions.